Cursed (or defective) Potions of Fire Breathing

The alchemist Quasit may be trying to make Potions of Fire Breathing and the formula is defective.  Instead, when imbibed it causes the drinker to burst into flames (save to take only 8d10 damage).  Of course, being the twisted soul that he is, he managed to weaponize it.  One of the constructs that the quasit builds has a special implement (that does 1d6 points of damage) that can inject just a little bit of one of these potions into a wound, as it calls for difficult-to-source components such as a special gland from a red dragon.  The implement can contain six doses, and has 1d6 doses available (minimum one).

On a successful attack the victim must save versus paralysis or a little bit of the potion is injected into the body cavity of the victim.  Once that happens over 2d6 turns the victim begins to feel warmer and warmer, until they begin to belch out smoldering blood and burn up from the inside suddenly, dying of spontaneous human combustion.  A Cure Disease or Neutralize Poison spell can negate the major harmful effects, relegating it to doing a simple 1d6 points of damage from the heat generated by the potion.